Subs that hit that low end bass

[bhsdriller 10+ year member]

05 xxx

 

[PV Audio 5,000+ posts]

Welcome! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

As said, you're misunderstanding the manufacturer's specs. I don't know if you're looking at Fs, which is the free air resonant frequency, (basically, take the sub out and put it on the ground, sweep from 0hz to 100hz and where ever it moves the most is the Fs) or the frequency response range. Regardless, these numbers are useless by themselves. You use the numbers, called Thiele-Small parameters (T-S parameters for short) to help you design enclosures around each speaker.

The reason why your subs are flapping is due to how a sealed enclosure works. Basically all that a sealed box does is use the speaker's own pressure to control how the cone moves. Because the air behind the cone is pressurized, as long as the speaker can keep that air pressurized, it will have sufficient output. At too high of a frequency, and obviously the speaker cannot even play it. At too low of a frequency, the speakers do not have sufficient energy to pressurize the air and what happens is known as "bottoming out" which is merely the speakers flapping in the air like you described because the pressure in the box is too low. That is, unlike what you think, more often an issue with the enclosure being too large for the amount of air pressure the speakers can produce at various frequencies. What I recommend that you do is to first build a smaller sealed box by about .1 to .2 cubic feet, and if you still do not like it, then build a ported box tuned around 30-35hz. That should help you hit lower frequencies that you like, and if you still aren't satisfied, then it might be time for some new subs! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

If you need help designing anything, feel free to PM me, but I can't guarantee I'll respond, but I will put you in contact with some of the best designers on the forum since I no longer do any designing for car audio //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

-Dave

 

[jkok7 10+ year member]

for shits and giggles, build a vented enclosure the 2 of the p3 that is tuned low and larger than rec spec and you will be crazy impressed.

check out how much air my 2 10" were moving...

http://www.youtube.com/user/96passportsq#p/u/0/BW8wB3wp1JA

Nice video! I like how the headrest was movin. I think I might be able to fit 3 P3s in my car, but I won't go down to 2.

 

[loud-n-low 10+ year member]

try adding polyfill. i run my sealed 12's in 1.75 with polyfill. lots of lows

 

[ciaonzo 5,000+ posts]

(basically, take the sub out and put it on the ground, sweep from 0hz to 100hz and where ever it moves the most is the Fs)

Not even remotely correct.

 

[PV Audio 5,000+ posts]

Not even remotely correct.

Engineering wise, it's where the impedance of the speaker is at its max. In speaker terms, its where the moving mass is in balance with the force of the suspension. I just use that definition since it's easiest to visualize. How would you make it simpler? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[jkok7 10+ year member]

You know polyfill might be my problem. With the kickers I had some polyfill filled in loosely about 25% of the chamber.

With the Rockfords I glued about an Inch of polyfill to every surface on the inside of each box. Again the boxes are already a little larger than recommended. So I might not need the Polyfill as the woofer is thinking the box is even larger than it is. Is that why i can't hit the notes I used to with the Kickers? Just a thought.

 

[loud-n-low 10+ year member]

You know polyfill might be my problem. With the kickers I had some polyfill filled in loosely about 25% of the chamber.
With the Rockfords I glued about an Inch of polyfill to every surface on the inside of each box. Again the boxes are already a little larger than recommended. So I might not need the Polyfill as the woofer is thinking the box is even larger than it is. Is that why i can't hit the notes I used to with the Kickers? Just a thought.

try it and find out

 

[PV Audio 5,000+ posts]

Take out the polyfill as all it does is fool the sub into thinking its enclosure is larger than it really is. If that doesn't work, try a smaller box //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[loud-n-low 10+ year member]

Take out the polyfill as all it does is fool the sub into thinking its enclosure is larger than it really is. If that doesn't work, try a smaller box //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

his goal is lower notes, this just seems to be the opposite of what many advise to do

 

[ciaonzo 5,000+ posts]

Engineering wise, it's where the impedance of the speaker is at its max. In speaker terms, its where the moving mass is in balance with the force of the suspension. I just use that definition since it's easiest to visualize. How would you make it simpler? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

That's much better. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif I figured you possessed the knowledge but didn't understand why you just wouldn't have said that instead.

The problem with the visual that you described is that if you take a driver (SQ type, higher Cms number) in free-air and apply a sweep at constant voltage, it should quadruple excursion for every octave halving, regardless of what the Fs is, up until the point that it reaches Xmech. That doesn't match your visual and could be misleading to new guys.

 

[jkok7 10+ year member]

his goal is lower notes, this just seems to be the opposite of what many advise to do

Yeah your right, the theory is "It takes space to make bass". And by having a sub think that an enclosure is bigger than it actually is, that should make it hit even lower notes. Well I remember hearing that sometimes it can backfire depending on how much polyfill you have in the box. Cause the too much makes the sub think the box is too small. So that might be my problem. I'm gonna try it tomorrow and see.

Thanks Yall!

 

[PV Audio 5,000+ posts]

his goal is lower notes, this just seems to be the opposite of what many advise to do

What poly-fill does is by taking up breathable space, when the speaker moves, it causes the fibers of the polyfill to vibrate and as such, some of the energy is disapated as heat. This increase in heat thus creates a lower air density for the speaker, and as such if you model the speaker as an airspring as I did in a few posts above, it fools the speaker into thinking there is more space than there really is. There are advantages: it can lower the rolloff point and allow the speaker to be more efficient. However, as a corollary, it causes the speaker to sometimes become less damped and can thusly lead to overexcursion, aka, bottoming out. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[PV Audio 5,000+ posts]

That's much better. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif I figured you possessed the knowledge but didn't understand why you just wouldn't have said that instead.
The problem with the visual that you described is that if you take a driver (SQ type, higher Cms number) in free-air and apply a sweep at constant voltage, it should quadruple excursion for every octave halving, regardless of what the Fs is, up until the point that it reaches Xmech. That doesn't match your visual and could be misleading to new guys.

I seem to learn something new every time I talk to you, thanks //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ciaonzo 5,000+ posts]

I seem to learn something new every time I talk to you, thanks //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

It seems your attitude is vastly improving every time I talk to you, which a is a welcome sign of maturity, so thank you. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

With regard to your description for the function of a sealed enclosure, take a quick refresher read on a driver's Vas and Qts and how varying a sealed enclosure's volume will impact them and ultimately, Qtc. You were very close on that one, save for a couple details concerning what I've mentioned. Look closely at the relationship between enclosure volume and driver Vas in particular.

You're too smart for your age. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif I know at 20, I didn't have a handle on Qts and such but that was because I was drinking/serving overseas. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif